The present invention relates a digital signal recording and reproduction apparatus for recording and reproducing a digital signal, or more in particular to a recording and reproduction apparatus suitable for recording and reproducing a digital compressed video signal.
In recent years, digitization of the broadcasting has been under way.
The use of the digital image compression technique has made it possible to transmit a plurality of programs at the same time in a frequency band that has conventionally been able to transmit only one program. In the digital image compression, the data format of the packets to be transmitted is predetermined. Data are transmitted, for example, in packets of 188 bytes.
On the other hand, standardization of the specification of the digital VCR (video cassette recorder) for recording the digital broadcasting is under way. In the case where the digital VCR is used, a program can be recorded and reproduced in digital form and image can be stored with high quality.
For example, JP-A-5-174496 discloses a digital signal recording and reproduction apparatus for recording a digital compressed video signal on a magnetic tape using a rotary magnetic heads.
In the above-mentioned digital VCR, although the format for recording on the magnetic tape is determined as a standard, the contents of the data to be recorded are not specified.
A digital broadcast receiving apparatus for receiving the digital broadcasting varies from one broadcasting station to another, and there are several types of interfaces connecting to the VCR. The same digital image compression scheme is often used with different additional information such as time information or time stamps.
The time stamp indicates the time interval at which packets are sent for transmitting or storing digital signals. Even in the case of a delay occurring during transfer, the correct packet intervals can be determined by adding the time stamp.
The intervals at which packets of the digital compressed video signal input from a digital broadcast receiving apparatus are transferred is not constant and have a temporal gap. In the case where this signal is recorded directly, there occurs on the recording medium an area where no data is recorded. In order to increase the recording capacity of the recording medium and save waste, packets are desirably recorded closely in packed state. In the case where the packets are recorded in packed state, however, data cannot be output in reproduction mode at the same timing as in recording mode unless the record includes information on the intervals at which the packets have been transferred. Also, even in the case where the packets are recorded loosely without packing, data are recorded in predetermined recording areas and therefore positions of the packets input are temporally displaced, thus making it difficult to output the reproduced data at exactly the same timing as at the time of recording.
In the case where data in the form of packets are recorded and reproduced by a recording and reproduction apparatus such as the VCR, a time stamp is added and recorded together with the packet data in advance and the packet output timing is regulated with reference to the time stamp at the time of reproduction. In this way, the packet data can be output at the same timing as at the time of recording.
As described above, in the case of recording and reproducing packet data by a recording and reproduction apparatus, addition of the time stamp is essential.
As an actual interface that has so far been conceived includes the one in which packet data in digital compressed signal of 188 bytes, for example, are transferred directly. In this system, the input signal contains no time stamp, and therefore a time stamp is added and recorded in the VCR in accordance with the timing at which the packets are input.
The VCR desirably records the time stamp in synchronism with the recording track position. For example, a reference signal is set to 27 MHz, the position on the recording track is expressed with 18 bits, and the recording track position is expressed with 8 bits, so that a total of 26 bits of information are added as a time stamp to the packets for recording. In this way, the position at which the packet data reproduced are located on the recording track can be determined, thereby facilitating the processing of the reproduced signal and variable-speed reproduction.
An interface has been conceived, on the other hand, in which a time stamp of 20 bits generated by a reference clock of 27 MHz is added to the digital compressed video signal of 188 bytes to transfer data. Assume that data are sent using this interface. Since the time stamp is added to the input packet in advance, the timing at which the packets ate output can be adjusted on the basis of the time stamp at the time of reproduction, as long as the data are recorded in the recording medium together with the time stamp. Also, in view of the fact that the time stamp added in advance is used, the VCR is not required to generate a time stamp and therefore no error is caused in the time stamp.
In the recording operations performed with equipment having different interfaces as described above, however, the difference in the format of time stamps causes different formats of data to be recorded on the tape, often leading to the loss of tape compatibility.
An object of the present invention is to provide a digital signal recording and reproduction apparatus which provides compatibility among recording media each recorded using a different digital broadcast receiving apparatus or makes possible reproduction from a recording medium recorded using a different digital broadcast apparatus.
According to one aspect of the invention, there is provided a digital signal recording and reproduction apparatus for recording digital signals on a recording medium in blocks together with a time stamp added to each packet for indicating the time of transmission of the packet having a predetermined number of bytes, comprising a reference signal generating means for generating a reference signal in synchronism with the input digital video signal, a time stamp generating means for generating a time stamp on the basis of the reference signal, a time stamp adding means for adding the time stamp generated by the time stamp generating means to the input digital video signal in place of the time stamp previously added thereto, a recording signal processing means for generating a recording signal in blocks from the digital signal, and a recording means for recording the recording signal in the recording medium.
According to another aspect of the invention, there is provided a digital signal recording and reproduction apparatus for recording digital signals on a recording medium in blocks together with a time stamp added to each packet for indicating the time of transmission of the packet having a predetermined number of bytes, comprising a reference signal generating means for generating a reference signal in synchronism with the input digital video signal, a time stamp generating means for generating a time stamp on the basis of the reference signal, a time stamp adding means for adding the time stamp generated by the time stamp generating means to the input digital video signal, a recording signal processing means for generating a recording signal in blocks from the digital signal, and a recording means for recording the recording signal on a recording medium.